French police arrest four over Lyon package bomb blast

The man's parents were later arrested and taken in for questioning, as was a second student of Algerian nationality who is a family relation, according the Paris prosecutor's office, which has jurisdiction over terrorism cases in France.

The suspect was previously unknown to police, Lyon's Mayor Gerard Collomb said.

He was arrested as he got off a bus, calmly putting his hands in the air when he spotted officers approaching, Collomb said.

The man's sister has also been questioned but she has not been arrested, prosecutors added.

Police had been searching for a man seen cycling near the scene of the blast wearing a green top and Bermuda shorts and carrying a dark-coloured rucksack.

He has been the target of an extensive manhunt since late Friday when an explosive device filled with screws and ball bearings was placed in front of a bakery near the corner of two crowded pedestrian streets in the historic centre of Lyon.

Police circulated photos of the suspect on Twitter, which they said led to "several dozen" calls from people with information.

- Victims hit with shrapnel -

Sources close to the investigation said the explosive was most likely acetone peroxide, or APEX, a volatile compound used in the deadly Paris terror attacks of November 13, 2015.

Investigators recovered small screws, ball bearings and batteries along with a printed circuit board and a remote-controlled trigger device. Officials later said the charge was relatively weak.

Thirteen people were wounded in the blast -- eight women, four men and a 10-year-old girl -- of whom 11 needed hospital treatment.

The Islamic State group has been behind many of the attacks. No one has claimed responsibility for the Lyon blast.